Diagnosis of pancreatic cancer

Abstract

The ability to diagnose pancreatic carcinoma has been rapidly improving with the recent advances in diagnostic techniques such as contrast-enhanced Doppler ultrasound (US), helical computed tomography (CT), enhanced magnetic resonance imaging (MRI), and endoscopic US (EUS). Each technique has advantages and limitations, making the selection of the proper diagnostic technique, in terms of purpose and characteristics, especially important. Abdominal US is the modality often used first to identify a cause of abdominal pain or jaundice, while the accuracy of conventional US for diagnosing pancreatic tumors is only 50-70%. CT is the most widely used imaging examination for the detection and staging of pancreatic carcinoma. Pancreatic adenocarcinoma is generally depicted as a hypoattenuating area on contrast-enhanced CT. The reported sensitivity of helical CT in revealing pancreatic carcinoma is high, ranging between 89% and 97%. Multi-detector-row (MD) CT may offer an improvement in the early detection and accurate staging of pancreatic carcinoma. It should be taken into consideration that some pancreatic adenocarcinomas are depicted as isoattenuating and that pancreatitis accompanied by pancreatic adenocarcinoma might occasionally result in the overestimation of staging. T1-weighted spin-echo images with fat suppression and dynamic gradient-echo MR images enhanced with gadolinium have been reported to be superior to helical CT for detecting small lesions. However, chronic pancreatitis and pancreatic carcinoma are not distinguished on the basis of degree and time of enhancement on dynamic gadolinium-enhanced MRI. EUS is superior to spiral CT and MRI in the detection of small tumors, and can also localize lymph node metastases or vascular tumor infiltration with high sensitivity. EUS-guided fine-needle aspiration biopsy is a safe and highly accurate method for tissue diagnosis of patients with suspected pancreatic carcinoma. (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) has been suggested as a promising modality for noninvasive differentiation between benign and malignant lesions. Previous studies reported the sensitivity and specificity of FDG-PET for detecting malignant pancreatic tumors as being 71-100% and 64-90%, respectively. FDG-PET does not replace, but is complementary to morphologic imaging, and therefore, in doubtful cases, the method must be combined with other imaging modalities.

Figure 1.

A 76-year-old man with pancreatic head carcinoma. CT revealed hypovascular tumor (arrow) in the head of the pancreas.

Figure 2.

A 60-year-old man with pancreatic head carcinoma. (a) CT performed at a local hospital revealed a low-density area (thick arrow) surrounding the superior mesenteric artery (thin arrow). The tumor was diagnosed as inoperable due to invasion to the superior mesenteric artery. (b) CT performed 2 weeks later revealed that the low-density area surrounding the superior mesenteric artery had disappeared. A low-density area surrounding the superior mesenteric artery was considered as corresponding to the acute inflammation of pancreatitis accompanied by pancreatic carcinoma. Invasion to the superior mesenteric artery was ruled out. (c) CT at a more cranial slice revealed that a tributary of the superior mesenteric artery (arrowhead) was involved in the tumor (thick arrow). (d) Three-dimensional reconstruction CT revealed that the tributary of the superior mesenteric artery involved in the tumor was a replacement common hepatic artery (arrowhead). Pancreatoduodenectomy combined with resection of the replaced common hepatic artery was performed. The common hepatic artery was resected between its root and the root of the proper hepatic artery (dotted line) and reconstructed in an end-to-end fashion.

Figure 3.

A 51-year-old woman with pancreatic head carcinoma. (a) Conventional CT performed at a local hospital revealed a low-density area in the head of the pancreas and the boundary to the portal vein was unclear (arrow). At that hospital, the tumor was diagnosed as inoperable due to portal vein invasion. (b) MPR (multi-planar reconstruction) images obtained by MDCT revealed that the portal vein was intact. Pancreatoduodenectomy combined with resection of the portal vein was performed. Histopathological examination showed no invasion to the portal vein (arrow).